Conventionally, soy milk is prepared by thoroughly soaking raw soybeans in water, pulverizing the soybeans to prepare a paste, and heating the paste obtained to not less than 100° C. for about 3 to 5 minutes. Recently, a variety of improved producing methods have been developed, along with a variety of soy milk products employing soy milk.
Since soy milk is more than half water, it has a high specific gravity and is problematic in that it requires time and effort to transport. Thus, it is costly to transport soy milk that has been produced in one factory to another factory for the production of a final product; there is a need to reduce this cost. Further, adequate sterilization at high temperature is necessary in the process of producing a final product using soy milk. There is also a need to simplify the equipment and operations required in the sterilization process. There is a further need to improve the quality and tastiness of the final product.
The present inventors conceived that such problems of prior art could be solved by preparing a powder serving as a starting material for soy milk, and then using that powder to produce soy milk products. That is, when a powder serving as a starting material for soy milk is produced in advance, transported to a processing plant, and used to produce a final product, not only can transportation costs be greatly reduced, but the space required by the processing plant can also be greatly diminished.
A number of producing methods have been proposed for powders to be used as starting materials for soy milk. However, when only a powdered starting material for soy milk is employed to produce soy milk products, it is impossible to obtain a quality, tasty product. Further, producing soy milk products still requires a high-temperature sterilization step, precluding the simplification of producing equipment and operations.
For example, Japanese Unexamined Patent Publication (KOKAI) Heisei No. 9-248129 discloses a method of producing powdered soy milk. The method disclosed in this publication is characterized in that the paste is heated at from 45 to 65° C. either instantaneously or for a period not exceeding 20 minutes, the lees are subsequently separated out to obtain soy milk, and the soy milk is spray dried to obtain powder. This method describes that tofu of good elasticity and flavor can be produced. However, soy milk is first prepared and then dried to obtain powder, so this method is not intended to provide a simple method of producing soy milk products. Further, the production of soy milk products requires a high-temperature sterilization step, so a highly tasty soy milk product is not necessarily achieved.
In light of these problems of prior art, the present invention has for its object to provide methods of producing soy milk product that are both simple and inexpensive. A further object of the present invention is to provide methods of producing high-quality and highly tasty soy milk products. A still further object of the present invention is to provide methods of producing soy milk products that do not require the high-temperature sterilization step that is essential in conventional methods.